Ultrasonic phased array technology provides an effective way to inspect composite wind turbine blades for flaws during manufacturing. Phased array probes use multiple piezoelectric elements that can be electronically controlled to generate beams for scanning blades. This allows for high resolution inspection and detection of flaws like porosity, disbonds, delaminations, and wrinkles. Automated scanning systems can inspect large areas quickly, generating C-scan images to analyze bond quality and adhesive thickness. Ultrasonic phased array offers productivity advantages over conventional UT for the critical task of ensuring blade integrity.

1. Improved Inspection of
Composite Wind Turbine Blades with Accessible,
Advanced Ultrasonic Phased Array Technology
André Lamarre (andre.lamarre@olympus-ossa.com)
Olympus Scientific Solutions Americas, Canada
12th ECNDT Conference, Gothenburg, Sweden, June 2018

2. Content
§ Description of wind turbine blades
§ How ultrasonic phased array inspection works
§ The detection capabilities of ultrasonic phased array technology
§ The productivity of ultrasonic phased array technology
§ Conclusions

3. Main Components of a Wind Turbine
§ Wind turbine blades
– Generate aerodynamic torque from the wind
§ Nacelle
– Converts the torque into electrical power
§ Tower
– Holds the nacelle and rotor blades
– Provides access to the nacelle
§ Foundation
– Ensures that the turbine stays upright
All these components require nondestructive testing to help ensure their integrity during
manufacturing, construction, and maintenance.
In this presentation, we focus on the use of ultrasonic phased array for inspecting wind
turbine blades during manufacturing.
Wind blade
Nacelle
Tower
Foundation

4. What Is a Wind Turbine Blade?
§ A turbine blade is composed of an outer shell that is reinforced by one or many
internal structural beams, also called spars
§ The number of spars depends on the size of the blade
§ The interior of the blade is hollow
§ Depending on the manufacturer, the spar could be an I-beam or a box

5. What Is a Wind Turbine Blade?
§ The I-beam spar is composed of 2 spar caps and one shear web
§ The box spar is composed of the 2 spar caps and 2 shear webs
§ The spar caps are attached to the the skin with adhesive
§ Materials
– Glass-reinforced fiber, carbon-reinforced fiber, balsam/wood, adhesive,
resins, honeycomb structures, and coatings
– Most materials are not acoustic friendly

6. Manufacturing Flaws
§ Flaws can be the result of the blade’s
design or occur during manufacturing
§ Types of flaws include:
– Porosity
– Disbonds
– Delamination
– Inclusions
– The width of the adhesive and its
position between the beam and
shell
– Wrinkles (out-of-plane waviness)

7. Principles of Ultrasonic Phased Array

8. Blade Inspection Using Ultrasonic Phased Array
4-element aperture 1 mm (0.039 in.)
§ Phased array probes are
composed of multiple
piezoelectric elements
§ Pulsing and receiving of the
elements is electronically
controlled to generate
beams
§ Blade inspection is
performed using linear scan
beams

9. Data Point Density
Low Density High Density
§ Higher density
§ Greater probability of detection
Missed Detected

10. Large Effective Beam
Conventional UT probe Phased array (64 elements)
Larger coverage in one pass
Finer resolution

11. Analysis Views
Amplitude
C-scan
A-scan
D-scan
B-scan

12. Olympus Phased Array Instruments for Wind Blade Inspection
OmniScan® SX
Flaw Detector
OmniScan MX2
Flaw Detector
FOCUS PX™
Acquisition Instrument
Manual and semi-automated inspection
Semi and fully-automated inspection
Portable
One PA probe
Portable
Multiple PA probes
PC-based
Multiple PA probes
Scalable

13. Low-Frequency Linear Phased Array Probes
§ Frequencies: 0.5 and 1 MHz
§ Number of elements: 64
§ Length: 96 mm
§ Elevation: 22 mm
§ Pitch: 1.5 mm
§ Plastic housing to reduce the weight

14. Low-Frequency Linear Phased Array Probes
§ Mounted on 4 different wedges/probe holders
§ One with a semi-contact probe holder for deep
penetration
§ One with an Aqualene delay line for improved near-
surface resolution
§ Both probe holders are available as either curved
or flat
§ All wedges/probe holders have water irrigation
and an encoder attachment

15. The Detection Capabilities of Ultrasonic Phased Array

16. Example of a Spar Cap Inspection
§ Uses an automated scanner
§ OmniScan MX2 flaw
detector
§ Olympus wind blade PA
probe and wedge
§ Results presented as an
amplitude C-scan
Superimposed image for
illustration purposes

17. § The C-scan below represents the ultrasonic mapping of the spar cap
Example of a Spar Cap Inspection
Bonded zones between the spar cap and shell
Cross section
Length
Cross section
Flanges
§ At CRP or GRP flanges, the ultrasound reflects off the inner side of the skin, resulting in
a strong echo (represented in red on the C-scan)
Nottoscale.Forillustrationpurposes
§ At bonded zones, if the bond is good, the ultrasound travels through the adhesive
and disperses into the web, resulting in no or weak echo at the bonded interface
(represented in blue or yellow on the C-scan)

18. § Using the amplitude C-scan image, we can:
§ Measure the width of the adhesive zones
§ Evaluate the quality of the bonds
§ Locate deficiencies in a bonded area
§ With the low-frequency phased array probe, the sizing resolution is 1.5 mm
Example of a Spar Cap Inspection
Bonded zones between the spar cap and shell
Cross section
Length
Cross section
Flanges
Nottoscale.Forillustrationpurposes.

19. Bonding Evaluation
§ In this example, the bonded zone is
deficient
§ The width of the bonded zone is getting
narrow
§ An 80 mm long section is totally
disbonded
§ Localized unbonded areas are also
present in the good area
– Approximate size: 20 mm × 20 mm

20. Adhesive Thickness Measurement
§ Depending on the adhesive material,
echoes from the interface shell’s glue and
the web’s glue are visible
§ The distance between these 2 echoes
characterizes the adhesive thickness
§ Using the right velocity, the adhesive
thickness can be evaluated

21. Delaminations
§ Delaminations between different
GRP or CRP
layers can be located
§ Good reflector of ultrasound
§ A time-of-flight C-scan is useful
to discriminate between a
geometry echo and
delamination
Delaminations
Delaminations

22. Detecting and Sizing Wrinkles
§ Wrinkles are an out-of-plane alignment
of layers
§ They reduce the blade’s tensile strength
§ Can create out-of-plane delaminations
§ Deviation in the vertical plane: 4 mm
§ Length of the wrinkle: 17 mm

23. The Productivity of Ultrasonic Phased Array

24. Using Automated Ultrasonic Phased Array to Inspect a Spar Cap Girder
§ OmniScan MX2 unit
§ Scanner length: 5 m; scanner
width: 0.5 m
§ Scanning direction: length of
the blade
§ Indexing direction: cross-
section of the blade
§ 100 mm indexing
§ Acquisition resolution: 1.5 mm
in both axes
§ 2 m2 inspected in 40 seconds
§ The C-scan and A-scan are
both recorded The scanner is not an Olympus product.

25. C-scan Representation
§ OmniScan MX2 unit
§ Scanning direction: cross-section
of the blade
§ Indexing direction: length of the
blade; 100 mm indexing
§ Live mapping on the screen
§ Bonded zones and flanges are
clearly visible

26. Conclusions
§ Ultrasonic phased array can be used to inspect wind blades with low-frequency
probes (0.5, 1 MHz)
§ The 1.5 mm resolution enables small flaws to be detected
and accurate flaw sizing
§ Flaws such as wrinkles, delamination, and disbonds can be detected and sized
§ The linear scan capability enables fast inspection while maintaining 100%
coverage of the part

27. Conclusions
§ Off-the-shelf phased array units can be used as a standalone or
integrated with automated scanners
§ C-scan imaging enables analysis at a glance
§ Use of A-B-C-D scans permit a more detailed interpretation
§ Data is archived
§ The use of ultrasonic phased array can also be considered in the maintenance
program of wind turbine blades

28. Thank You
Olympus and OmniScan are registered trademarks, and FOCUS PX is a trademark of Olympus Corporation.